A prior art frost-proof valve is shown in DE 202 19 008, the entire disclosed content of which is hereby included by reference for the purpose of disclosure. In this prior-art frost-proof exterior-wall valve, frost resistance is achieved by ventilating the interior of the valve device via a ventilation valve after the main valve has been closed. The ventilation valve of the prior-art valve device is a spring-loaded valve, which closes due to the internal pressure of the valve device when the main valve is open, and with decreasing internal pressure is moved into the open position by a pressure spring, allowing air to access the valve interior and causing water contained therein to drain via the discharge opening.
This valve device can allow reliable frost-proof operation. However, the inventor has determined that it can be further improved.
For valve devices connected to the public water supply network in the area of potable water supply, it is of advantage, and in some countries even required by statutory regulations, for a backflow prevention valve to be present, which serves to prevent feeding contaminated water into the water supply network through the valve against its flow direction. Such backflow prevention valves are usually embodied as spring-loaded check valves. However, when balancing the spring force of such a backflow prevention valve and of the ventilation valve of the prior-art frost-proof exterior-wall valve, it can be a challenge to balance the spring forces to achieve both a reliable backflow prevention on the one hand and a reliable opening of the ventilation valve in the un-pressurized state on the other.
There exists a need to further develop this prior-art valve, so as to guarantee frost-proof exterior use and at the same time to allow coupling a backflow prevention valve with the valve device or integrating it into the valve device, without creating any adverse effects on functionality.